A communication system operates to provide for the communication of data between communication stations positioned at spaced-apart locations. At least one of the communication stations forms a sending station, and at least another of the communication stations forms a receiving station. A communication channel interconnects the sending and receiving stations. Data is communicated by a sending station to a receiving station by way of the communication channel.
Various types of communication systems have been developed and deployed, capable of effectuating different types of communication services. As a result of technological advancements, new types of communication systems have been developed and deployed. With continued technological advancements, additional types of communication systems shall likely be developed and deployed, providing improved and new communication services that can be effectuated.
A radio communication system is an exemplary type of communication system. Various types of radio communication systems have been developed and deployed, permitting the effectuation of many types of communication services. Radio communication systems utilize communication channels that are defined upon radio links formed between sending and receiving stations. The need otherwise to utilize wireline connections along the entire paths between the sending and receiving stations is obviated. That is to say, at least for the portion of the path that utilizes radio communication channels defined upon a radio link, the need for a wireline connection is obviated.
Use of a radio communication system by which to communicate provides various advantages. For instance, the costs required initially to deploy a radio communication system are generally less than the costs required to deploy a corresponding wireline communication system. That is to say, the infrastructure costs associated with a radio communication system are generally less than the infrastructure costs associated with a corresponding wireline communication system. Additionally, a radio communication system is amenable for implementation as a mobile communication system in which communication mobility is provided to one or more of the communication stations operable in the communication system.
Many radio, as well as other, communication systems make use of digital communication techniques. And, many of the technological advancements that have been implemented in communication systems pertain to digital communication techniques or provide for the communication of the data in digital form. When digital communication techniques are used, data that is to be communicated is first placed into digitized form. And, then, typically, the digitized data is formatted into data packets or frames according to a selected data formatting scheme. The data is communicated by sending the packets or frames between the sending and receiving stations. Because of the formatting of the data into packets or frames, the packets or frames can be communicated individually or in discrete groups. And, when delivered to the receiving station, the informational content of the data is recovered by determining the values of the data contained in the packets or frames.
Ideally, the data is communicated upon distortion-free channels so that the values of the data, when received at a receiving station, are in identical correspondence with the values of the data when communicated by a sending station upon a radio channel. However, in an actual system, fading, or other distortion-causing conditions distort the data during its communication upon the channel to the receiving station. If the values differ significantly, the informational content of the data can not be recreated at the receiving station. Fading conditions, also know as multipath conditions, alter the values of the values of the data, or portions thereof, such that, when detected at the receiving station, the values of the data differ with corresponding values when sent by the sending station.
Compensation for the distortion caused by fading is attempted by various techniques. For instance, the diversity of the data is sometimes increased to increase the likelihood that the informational content of the data is recovered at the receiving station.
One type of diversity is time diversity that is introduced into the data that is communicated by a sending station. By utilizing time diversity, time redundancy is introduced into the data. By introducing time redundancy, loss of portions of the data during its communication upon a channel susceptible to fading is less likely to prevent recovery of the informational content of the data. The time diversity takes advantage of the time variance typically associated with fading. That is to say, the amount of fading varies as a function of time, and the time diversity introduced into the data that is communicated upon such a channel increases the likelihood that some part of the redundant data is delivered to a receiving station.
Space diversity is sometimes also utilized. In space diversity, a sending station uses two or more transmit antennas from which to transmit data that is communicated to a receiving station. The transmit antennas are spaced apart by separation distances, thereby to cause the data that is communicated by the respective ones of the transmit antennas to be communicated upon differing communication paths to the receiving station. Through appropriate selection of the separation distances, the correlation between the data is potentially reduced. Systems that utilize multiple transmit antennas are sometimes referred to as being multiple output systems. Spatial, and sometimes also polarization, diversity is provided in systems that utilize multiple transmit antennas.
As the data rates, and corresponding amounts of data, that must be communicated to effectuate many new, and proposed communication services increases, the need to utilize multiple output communication systems shall also become increasingly necessary due to the increased throughput capabilities of the multiple output systems. As data shall need to be communicated upon channels that are susceptible to fading, or other distortion-causing conditions, there shall be a continuing need to utilize diversity in the communication of the data.
If an improved manner could be provided by which selectably to increase, or otherwise alter, the amount of diversity introduced upon data that is to be communicated, depending upon communication conditions, improved communications would be possible.
It is in light of this background information related to the communication of data in a communication system susceptible to fading, or other distortion-causing conditions, that the significant improvements of the present invention have evolved.